Various attempts have been made to produce epoxide resin compositions with improved mechanical properties. Examples are described in U.S. Pat. Nos. 3,297,622, 3,316,195, 3,806,483 and 4,128,519. A paper by Trostyanskaya, Babayevskii and Kulik in "Polymer Science U.S.S.R." Vol. 21 pp 1456-1462 describes how epoxidised rubber latices can be incorporated into an epoxide resin using the compatibility provided by the epoxide functional groups and then co-reacting with these functional groups to produce a bonded matrix. Other attempts to improve the mechanical properties of epoxide resins have involved the incorporation of liquid nitrile rubber or the use of particular curing agents. However, the resulting compositions usually have inferior ultimate strength and a lower heat distortion temperature than unmodified resins.
The flammability of epoxide resins has been reduced by incorporating a halogen into the backbone of the resin structure, for example by the use of brominated bisphenol-A in the reaction mixture for producing the resins. Alternatively, conventional fire-retardants such as halogenated compounds, aluminum trihydrate, antimony compounds or phosphorus compounds may be incorporated in the resins. These additives, however, may have undesirable effects on other properties, for example lowering the heat distortion temperature.